On the stackoverflow, there is a add comment functionality, which is done using ajax. I'm curious to know how that works. I understand that on add comment button, a ajax post request is sent to the server, but from his point I'm stuck.

Can u explain me how it works or send me to some web resuorces which explains it?

1) Sends the data back to the server via AJAX to be stored in the database and returns an "okay" back to the browser if the comment is successfully added/stored.2) When the browser gets the "okay" response from the server via AJAX, another javascript function appends the data/text/comment to the existing HTML without having to reload the entire page. If the browser does not get the "okay", the user may see an error message displayed instead.